Volume 14, Issue 11, 01 June 1969
Index of content:
14(1969); http://dx.doi.org/10.1063/1.1652675View Description Hide Description
Laser emission has been obtained in Pb1−x Sn x Se diodes with x up to 0.28, and the temperature dependence of the emission has been studied in the range from 1.5 to 100°K. The results strongly support a band model in which the conduction and valence band edge states cross as the Sn content is increased from 0 to 0.28. For x ≤ 0.10, the temperature coefficient of the energy gap is positive whereas for x ≥ 0.19, the temperature coefficient is negative as predicted by the band model. Also, the results provide evidence that the energy gap is direct on both sides of the crossover point which at 4.2°K occurs for x ≈ 0.15.
14(1969); http://dx.doi.org/10.1063/1.1652676View Description Hide Description
14(1969); http://dx.doi.org/10.1063/1.1652677View Description Hide Description
Power of 20 mW and gain of 11% have been obtained by using thermally excited nitrogen to pump a flowing‐gas carbon dioxide laser. One immediate use of this new pumping technique is the study of molecular laser physics in a simplified environment; the thermal laser is essentially free of chemical and charged‐particle effects.
14(1969); http://dx.doi.org/10.1063/1.1652678View Description Hide Description
The method of ``live‐fringe'' holographic interferometry has been adapted for use on transmission objects with two ruby lasers replacing the customary cw laser. The hologram is produced with a giant pulse laser and reconstructed with another laser having a pulse width of 50 μsec. Consecutive, real time interferograms can be obtained during this period with image convertercameras pulsed on for as little as 0.1‐μsec intervals.
14(1969); http://dx.doi.org/10.1063/1.1652679View Description Hide Description
The ionization rates of GaAs are first empirically determined from breakdown voltage measurements of p +‐n junctions with thick n layers. The theoretical analysis is then extended to p +‐n‐n + structures in which space‐charge punch‐through occurs before breakdown takes place. The avalanche breakdown voltages of GaAs p +‐n‐n + diode structures are calculated as a function of the n layer thickness W as well as the doping density n. Comparison of the theoretical calculation with experimental data shows very good agreement.
ELECTRICAL RESISTIVITY MODEL FOR POLYCRYSTALLINE FILMS: THE CASE OF SPECULAR REFLECTION AT EXTERNAL SURFACES14(1969); http://dx.doi.org/10.1063/1.1652680View Description Hide Description
A model is developed for estimating effects due to electron scattering from grain boundaries, occurring simultaneously with background scattering. Since grain‐boundary effects are negligible in bulk materials, the model is particularly relevant to polycrystalline metal films in which a very fine‐grained structure is often found. It is shown by solution of the appropriate Boltzmann equation, that the total resistivity can be strongly dominated by grain‐boundary scattering. If grain size increases with film thickness, a marked dependence of resistivity on thickness exists, even when scattering from external surfaces is negligible or is completely specular.
14(1969); http://dx.doi.org/10.1063/1.1652681View Description Hide Description
Continuous‐wave laser oscillation has been observed in pure helium at wavelengths of 95.8 and 216.3 μ corresponding to the 31 P → 31 D and 41 P → 41 D transitions, respectively. Study of the excitation mechanism of the laser levels permits calculation of gain and output power starting from first principles.
14(1969); http://dx.doi.org/10.1063/1.1652682View Description Hide Description
Iron borate (FeBO3) is a transparent, green, uniaxial, canted antiferromagnet with a Curie temperature of 348°K. The optical absorption in the samples observed has a local minimum of 39 cm−1 in the green (5250 Å). The Faraday rotation at 5250 Å is 2300° per cm. The phase retardation associated with the uniaxial birefringence is about 4 × 105 per cm and the two indices of refraction are about 2.1 for the visible spectrum.
14(1969); http://dx.doi.org/10.1063/1.1652683View Description Hide Description
Iron borate (FeBO3) is a transparent, green, room‐temperature weak ferromagnet (a canted anti‐ferromagnet) with a Curie temperature of 348°K. Ferromagnetic resonance measurements, i.e., linewidth,anisotropy fields, and g factor vs temperature and frequency are reported for the first time on this material. A low‐temperature linewidth maximum of unknown origin is also observed. Its narrow linewidth, large magnetic anisotropy, large optical Faraday rotation, and transparency in the green (the latter two reported elsewhere) made FeBO3 of interest for devices such as electronically tunable cavities and filters up to ∼100 GHz and high‐speed magneto‐optic modulators.
14(1969); http://dx.doi.org/10.1063/1.1652684View Description Hide Description
Difference in the macrostructure of vapor‐deposited B and SiC filaments have been related to the extent of reaction between the deposited material and its tungsten substrate. Chemical reactions between W and B during deposition create mechanical dilatations of sufficient magnitude to produce radial cracks in the B sheath running the length of the filament. Similar reactions between W and SiC do occur but such cracks do not form because both the amount of the reactant is less and the corresponding volume expansion is significantly smaller.
14(1969); http://dx.doi.org/10.1063/1.1652685View Description Hide Description
Electron‐excited Auger spectroscopy, as it is presently applied, utilizes incident beam energies which are normally greater than that corresponding to the maximum ionization cross section. Preliminary measurements indicate that Auger emission at these high primary energies is significantly enhanced due to excitation by internal secondary electrons. This creates a serious problem with respect to the use of Auger spectroscopy as an analytical tool.
14(1969); http://dx.doi.org/10.1063/1.1652686View Description Hide Description
We have observed tunable four‐photon optical parametric noise in calcite with a Q‐switched rubylaser pump. The observed radiation corresponds to the spontaneous emission from a phase‐matched parametric system satisfying the relations: (1a) ω(ruby) + ω(ruby) = ω1 + ω2 and (1b) , where ω and k denote the angular frequency and wavevector, respectively. The superscripts o and ε denote ordinary and extraordinary rays, respectively. The optical signal was tuned from 4300 to 5860 Å by adjusting the orientation of the calcite; this signal was detected by an RCA 7265 photomultiplier. Although no direct detection of the infrared signal was attempted, we would expect it to be tuned over the range from 0.843 to 1.80 μ. From experimental data, the estimated noise power in the high‐frequency optical signal was about 0.5 μW.
14(1969); http://dx.doi.org/10.1063/1.1652687View Description Hide Description
Hyperfine components of the R(127) line of the 11–5 band of molecular iodine at 633 nm have been observed by saturating the absorption inside the cavity of a single‐frequency He–Ne laser. The component widths of 4.5 MHz were broadened a factor of 2 by 1‐Torr iodine pressure, or by 500‐G magnetic field. Since no wavelength shift as large as 2 MHz was observed, wavelength perturbations from these sources should be controllable to less than 2 × 10−13λ. The use of one of these components as a reference for laser stabilization is suggested.